1. Field of the Invention
The present invention relates to a probe device and a method of controlling the device. More specifically, the present invention relates to a technique of carrying out: evaluation of local electrical conductivity of a nano-electric device surface; evaluation of an electrode of a nano-scale biological chip; research of a nano-region surface electrical conductivity; measurement of single molecule electrical conductivity; measurement of electrical conductivity of a single micro-crystal; evaluation of electrical conductivity of a domain critical interface; evaluation of electrical conductivity of a self-organized film; measurement of electrical conductivity of a single cell; and the like.
2. Description of the Related Art
Conventionally, evaluation of a local structure or electrical conductivity of a sample has been carried out by using a contact mode atomic force microscope which uses an electrically conducting probe (hereinafter, referred to as a “probe”). In this method, since the sample is scanned while the probe and the sample come into contact with each other, a certain degree of breakage occurs with both of the sample and probe. In a sample having a nano-scale structure, this breakage is fatal. Therefore, this contact mode measuring method cannot be applied to the sample having the nano-scale structure.
On the other hand, a tapping mode measurement is prevailingly known as a technique of evaluating only a structure. By means of this measuring method, measurement at a nano-scale resolution has been easily carried out. In this method, a cantilever is vibrated, thus making it possible to significantly reduce interaction between the probe and the sample, and further, measurement can be carried out without breaking the probe and the sample. In this method, however, a sufficient electrical contact cannot be obtained as compared with the contact mode measuring method. Therefore, this method cannot be used for evaluation of electrical conductivity in nano-scale.
Based on these restrictions, evaluation of local electrical conductivity in nano-scale is carried out as follows. First, structural measurement is carried out at a high resolution by using a tapping mode. Then, based on an image obtained by tapping mode measurement, the probe is moved to a predetermined position, the probe is pressed against the sample surface, and a current-voltage characteristic at the position is measured in a point contact condition. In this method, however, an intended position and a measuring point are shifted by a piezoelectric drift, thus making it impossible to precisely know a relationship between the structure and conductivity.
As has been described above, there has been no method for reliably measuring and evaluating local electrical conductivity of a sample having a nano-scale structure, and there has been a demand for an invention of a novel method.